<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
    var maxProfit = function(prices) {
        return prices.reduce((profit,currentPrice,index,prices) =>
                index>0 && currentPrice > prices[index-1] ? profit + currentPrice-prices[index-1] : profit,0);
    };
    let stock = [7,1,5,3,6,4];
    console.log(maxProfit(stock));
    
</script>
</html>